Abrasive article and method of making



Nov. 18, 1947. cs. J. GOEPFERT ETAL 3 35 ABRASIVE ARTICLES AND METHOD OF IAKING Filed June 12. 1945 mmvmas toeeE ozkrszr BY must? rv. WELL.

Jffor j Patented Nov. 18, 1947 UNITED STATES.

PATENT OFFICE ABRASIVE ARTICLE AND METHOD or MAKING of Delaware Application June '12, 1945, Serial No. 598,982

This invention relates to endless abrasive belts formed from strips of flexible, abrasive coated web material. More particularly, it is concerned with the belt splice or joint formed by adhesively uniting the ends of the abrasive strip, and with 5 vegetable glues, latex, phenol formaldehyde resins The in venticn is further pertinent to similar abrasive coated the adhesive for uniting said ends.

articles in which a continuous abrasive surface is obtained by adhesively joining contiguous ends 8 Claims. (01. 51-188)- To accomplish the ends in mind, efforts heretofore have been directed to the use of more complicated joint structures. having included such adhesives as animal and and the like. The earlier glue adhesives are not of suflicient strength or flexibility and as a result a. high percentage of them fail before the abrading lift of the belt expires. While some improveof abrasive sheet material to form article's having ment in strengthhas been obtained by the use of endless abrading surfaces, such as cones, cylin-.{

, drical drum covers andthe like.

Endless abrasive belts and the like'are commonly formed by adhesively splicing or joining the ends of a flexible, abrasive coated Web material. The joint may be one of a number of different types, as for example, that formed by bevj Another form of belt joint or splice is obtained by skiving' the end areas of the abrasive strip material free of abrasivefapplying adhesive to the one abrasive-cleared area and to the underside of the abrasive-cleared area at the opposite end of the strip, overlapping the two ends, pressing together and allowing the adhesive to set. Regardlessof the particular type of joint or splice employed, it is desirable to provide an adhesive therefor which will be quick-acting and also will result in a strong and flexible joint, and which is also satisfactory from the standpoint of staphenol formaldehyde resins and the like, and latex adhesives have resulted in somewhat higher flexibility, no belt joint has heretofore been found completely satisfactory in possessing the desired combination of behavior and properties. 'Moreover, certain. difliculties of application, such as extended periods of cure,'ren'der the useoflsom adhesives undesirable or uneconomical.

. More recently} it has been proposed to use certain urea aldehyde resin adhesive compositions as a bonding means in the joints of endless abrasive belts and like products. Although such compositions have been found satisfactory for use from the standpoint of rapidity of cure of '.the

adhesive and thestrength of the resulting joint.

their. use has been handicapped by the undesirablepropertysuch compositions have shown of instability upon standing. In other words, such urea aldehyde adhesive compositions when once prepared have had to be used within a relatively short time thereafter in order that the full strength of adhesion might be obtained. This deterioration in the adhesive characteristics of such compositions has been found to be a gradual bility, that is, an adhesive which will have a rea- 3 e d consequent y the u ti ate stren ths of sonably long, active adhesive life before subjection to cure whereby it can be prepared for use and will remain stable and active adhesively for a prolonged perio'd\of time and will not have tobe' processed in a matter of a few hoursafter its preparation.

Hitherto, most abrasive belt failures have been the result of a defective or weak joint or splice.

belt joints embodying such adhesives have been undependable in that they varied from belt to belt with the result that many belt joints so made,

after being accepted as of apparently adequate I (strength, have failed later under ope-rating conditions. t

It is therefore an object of the present invention to provide an improved belt splice which can During the constant d e at d flexing of the binexpensively and easily made, which will be of belt joint in abrasive operations by the passage of the belt joint around the pulleys and under the work being ground, the .belt joint has failed by a separation or delamination of the adhesively Considerable effort has been ;ingP

joined ends. directed to providing a belt joint which would be not only inexpensive and easily made, but which de ndablehigh strength and, will also obviate to 7 large degree the former difliculties and dis- ,advantage's encountered in belt splices and in the fabrication thereof under normal factory operat- In accordance .with the present invention abrasive belt splices are formed in whichthe two The bonding means employed 1 would have the requisite. strength and flexibility .,abrasives cleared and beveled or skived termini to stand up under constant and repeated flexing action for the normal abrading life ofthe belt. rial are adhesively united by means of an interof a, flexible abrasive coated sheet or strip mate 3 vening coating of an adhesive comprising a urea aldehyde condensation product which has been modified by the inclusion therewith of a minor amount of a cure retardant such as furfuryl alco- 'hol, together with a small amount of a suitable wetting agent. The use (if plain urea aldehyde condensation'products for such purposes is not desirable because of their inherent brittleness and lack of flexibility, and such use is not herein -claimed. Also, certain modified urea aldehyde condensation products have been found unsuited for present purposes because of the instability of their adhesive activity and the consequent lack of dependability of abrasive belts and the like embodying them as the joining cements. However, it has been found that when urea aldehyde condensation products are properly stabilized by the inclusion of a suitable cure retardant such as furfuryl' alcohol and a small percentage of a wetting agent such as that known and sold under the trade-mark Tween #20 therein, a beltjoint is obtained which is uniform and dependable and adhesive layer 8 serves the two ends in position.

Urea aldehyde adhesives which have been found to be highly satisfactory for belt joints have been obtained bymodifying catalyzed urea aldehyde condensation products by the inclusion therewith of from 0.5 to.5% of furfuryl alcohol as a cure retarding agent together with' the incorporation in the urea aldehyde condensation product of a small amount of a wetting agent. The addition of 0.5% of a wetting agent such as that known and sold under the trade-mark Tween (which is a sorbitan monolaurate polyoxyalkylene derivative) has been found to give satisfactory results. Other wetting agents which may be used include thosesold under the trade-marks Aerosol OT (dioctyl ester of sohas a high strength and flexibility and does not dium sulfo succinic acid), Triton W (a sulfated aromatic ether alcohol), Span 20 (sorbitan monolaurate), and Tergitol 08 (sodium salt of a higher secondary alkyl sulfate). The resulting reaction products produce belt joint adhesives of high stability in adhesive action so that the resulting adhesives can be employed to make dependable abrasive belt joints for as long as 48 hours or more after preparation of the adhesive. Moreover the above described adhesives provide joints of uniform high strength and flexibility satisfactorily madein accordance with the invensplice shown in Figure 2.

Referring further to the drawing, the coated abrasive sheet or web material 2 is first slit into appropriate widths and then cut to length. This coated abrasive sheet material comprises a suitable flexible backing 3, such as paper or cloth, to which is adhesively secured a layer 4 comprising abrasive grains, such as granular aluminum oxide, silicon carbide, or other granular abrasive material, bonded to the backing 3 by any suitable adhesive substance, such as glue, resins, or the like, singly or in combination. The end or cross cut 5 is usually made at an angle to the lengthwise direction of the strip as shown in Figure 3, but this is not a limiting condition as the cut 'could be made normal to the lengthwise direction. In the actual preparation of the splice narrow areas at the ends of'the abrasive-coated strip are beveled in the manner shown in Figures 1 and 2. The beveled surface 6 at one end of the abrasive strip is on the under side of the strip material and equal in area to the abrasive-cleared and beveled top surface area I at theopposite end of the abrasive strip. After the two ends have been skived and beveled, one or both of the beveled surfaces 6 and I are given a thin coating 8 Of modified urea aldehyde condensation product containing furfuryl alcohol and a wetting agent. The beveled areas are then superimposed as shown in Figure 2 and subjected to pressure and heat to form the joint 9 in which the intervening capable of withstanding the constant flexing action encountered in the use of abrasive belts and like products wherein splices are essential.

The initial reaction products of a urea with a methylene-containing body are obtainable in the form, of aqueous solutions or suspensions, which products when spread into a film and heated pass quickly and directly to the final, cured state and require temperatures and/or periods of cure substantially lower than those required to heatharden the phenolic resins. They are obtainable in a considerable number of. varieties, depending upon the specific urea compound employed, the relative proportion of the urea body and the methylene-containing body which are initially reacted, and the type of catalyst employed in bringing about the reaction. While our invention is not limited to any particular type of such resin, we have found that it is generally desirable to employ an initial reaction product which is not heat-hardening unless mixed with a separate liquid which acts as a catalyst and hardening agent for the reaction product and which matures quickly and directly to the final cured state when spread into a film, and to include a minor amount of furfuryl alcohol as a cure retardant to increase the adhesive stability of the cement, and a small amount of a wetting agent to increase the strength of adhesion of the cement to the cemented belt surfaces.

I The usual urea condensation products are obeither an acid or basic catalyst, it is generally believed that the latter product is obtained in colloidal form suspended in water. The reaction may be stopped by bringing the liquid to approximately the neutral point where it is neither acid nor alkaline. Such a product ma'y'then be made to securely unite and hold of ammonia and ammonium sulphate.

pounds, such as an ammoniacal solution of ammonium sulphate in water, or in fact, an ammoniacal solution of any ammonium salt which will give an acid reaction in water, may be employed to bring about the reaction of the initial product to the final infusible condition. Various aikyl derivatives of ammonia ma be used instead of ammonia, in preparing the hardening agent. Such compounds have the advantage that the fumes evolved therefrom when the articles are heated are less objectionable than ammonia.

It has been further found that the ammoniacal solution of ammonium sulphate in water and the alkyl derivatives of ammonia which are used as catalysts or hardening agents for the urea condensation products can be replaced by certain organic materials such as organic phosphates and the like which are very satisfactory for the purpose. That material sold under the trademark Bakelite XK-l5256 is a commercial organic phosphate available on the market and suitable for use as a hardener in practicing .the present invention.

We have found that an improvement in the adhesive stability of urea aldehyde condensation product cements when used as the adhesive in endless abrasive belt joints and the like obtained by the inclusion of from'0.5 to of furfuryl alcohol in the adhesive composition as a cure retardant and stabilizer for the adhesive. The exact amount of cure retardant used will to some extent depend upon the amount and type of catalyst used in conjunction with the urea aldehyde condensation product. The further addition of a small amount of a wetting agent enhances the strength of adhesion of such adhesive composition to the belt surfaces being joined. We have been able, by the use of 1% furfuryl alcohol together with the use of 0.5% of a wetting agent such as Tween #20 (defined hereinabove) to provide a satisfactory high strength urea aldehyde adhesive composition in belt joints which has suiilcient stability to remain adhesively active for longer than 48 hours. By contrast the urea aldehyde adhesives hitherto used for the purpose were unsatisfactory unless used the same day they were prepared,

The following specific examples are offered by way of illustration only, and given in detail the manner in which the invention is practiced and the nature of the adhesive used to form the belt joint.

Example I Parts by weight Liquid heat-hardenable urea-aldehyde condensation product, such as the urea-formaldehyde resin sold under the trade-mark Bakelite XRU-13108 100 The urea resin is an aqueous suspension of a urea-aldehyde condensation product containing 60% solids.

The adhesive-coated ends arethen airor force-dried, assembled and. pressed in a warm clamp having a temperature of about F.

for 20 seconds, following whichthe joined parts are removed and clamped in a hot clamp having a temperature of about 300 F. for 20 seconds.

Example II An abrasive belt joint was made monical solution of ammonium sulphate, con

taining 22% free ammonia and 10% ammonium sulphate. r

It is not desired to be limited to the type of belt joint or splice shown, as the invention can be practiced with any type of splice where two abrasive coated strips or sheets are adhesively united to. provide a continuous, flexible abrasive surface. For example, joints or splices can be made by skiving the abrasive from two end portions of an abrasive strip and overlapping the two cleared ends with a layer of intervening adhesive. Likewise V-shaped splices, or joints having various other configurations, can-be made in which thefurfuryl alcohol-modified urea condensation products as above set forth can be employed as the combining means to produce an improved splice. Likewise, the invention is not to be considered as limited to the specific adhesive compositions of the examples given.

In the claims we have used the word urea" to include both ordinary urea and derivative or substitution products of urea such as thiourea and the like.

Similarly, other forms of apparatus for applying heat and pressure other than the heated clamps set forth in the examples may be used, such as hot presses, mandrels or rolls.

While we have described our invention with particular reference to certain specific examples, it will be understood that other equivalent materials may be employed, together with other modifications and embodiments common to the art. The invention is therefore not to be restricted to the specific steps and materials herein de-v scribed, but rather is to be considered as of the scope defined in the appended claims.

We claim:

1. An endless abrasive article of manufacture as described.

, in Example I except that in preparing the adhesive therefor the Bakelite XKU-l2435 hardening constituent was replaced by reaction product of a mixture comprising a mauct, 0.5 to

v uct, approximately 1% not, approximately 1% jor proportion of a water-soluble urea aldehyde condensation product, a mirror proportion of furfuryl alcohol, and a small amount of an organic wetting agent which depresses the surface tension of the adhesive with respect to the web material.

3. An endless abrasive article of manufacture of flexible, abrasive-coated web material having a joint formed by two adhesively joined end portions, the adhesive of said joint comprisingsthe reaction product of a mixture comprising a water-soluble urea aldehyde condensation prodfurfuryl alcohol, and a small amount of an organic wetting agent which depresses the surface tension of the adhesive with respect to the web material.

4. An endless abrasive article of manufacture of flexible, abrasive-coated web material having a joint formed by two adhesively joined end portions, the adhesive of said joint comprising the reaction product of a mixture comprising a water-soluble urea aldehyde condensation prodfurfuryl alcohol, and approximately 0.5% of an organic wetting agent which depresses the surfacetension of the adhesive with respect to the web material.

5. An endless abrasive article of manufacture of flexible, abrasive coated web material having a joint formed by two adhesively joined end portions, the adhesive of said joint comprising the reaction product of a mixture comprising a water-soluble urea aldehyde condensation prodfurfuryl alcohol, and approximately 0.5% of a wetting agent such as a sorbitan monolaufate polyoxyalkylene. derivative.

6. An endless abrasive article of manufacture of flexible, abrasive-coated web material having a joint formed by two adhesively joined end portions,,the adhesive of said joint comprising the reaction product of a mixture comprising a water-soluble, acid-catalyzed urea aldehyde condensation product, 0.5 to 5% ofqa cure retardant such as furfuryl alcohol, and approximately 0.5% of an organic wetting agent which depresses the surface tension of the adhesive with respect to the web material.

7. In the process of forming endless abrasive articles the step which comprises adhesively uniting the end portions of an abrasive sheet material by means of an intervening layer of an adhesive comprising a water-soluble urea aldehyde condensation product, 0.5 to 5% furfuryl alcohol,

and a small amount of an organic wetting agent which depresses the surface tension of the adhesive with respect to the sheet material.

8. The method of forming endless abrasive articles which comprises removing the abrasive from an end of a flexible abrasive sheet, applying a liquid adhesive comprising a mixture of a water-soluble urea aldehyde condensation product, 0.5 to 5% of a cure retardant such as furfuryl alcohol, and a small amount of an organic wetting agent which depresses the surface tension of the adhesive with respect to the flexible sheet, to a terminal portion of the abrasive sheet, drying the liquid adhesive, overlapping the terminal portions with the adhesive therebetween, and applying heat and pressure to set the adhesive.

GEORGE J. GOEPFERT. HALSEY W. BU'ELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

